Electrical relay



Dec.- 14, 1943. H. a. WlTMER ELECTRICAL RELAY Filed June 11, 1941INVENTOR a m m G m m H 5&

HIS ATTO RN EY Patented Dec. 14, 1943 UNITED STATES PATENT OFFICEELECTRICAL RELAY Harold G. Witmer, Edgewood, Pa., assignor to The UnionSwitch & Signal Company, Swissvale, Pa., a corporation of PennsylvaniaApplication June 11, 1941, Serial No. 397,587

6 Claims.

My invention relates to electrical relays, and it has particularreference to tractive armature type electrical relays of the classemployed as track relays in railway signal systems.

An electrical relay having a pivoted tractive armature, when employed asa track relay in a railway track circuit where it is controlled by theapplication of a train shunt of low resistance across its winding, isrelatively quick in picking up but is comparatively slow in releasing.These characteristics are in a large measure due to the fact that theenergy required to pick up the armature of the relay is considerably inexcess of the energy required to hold such armature in its attractedpositioned after it has picked up. Such a relay must, of course,bedesigned to create its pick-up energy level, at least, in order toinsure that the relay armature will be picked up properly, and as aresult once this armature has reached its attracted position, the energylevel in the relay then exceeds by a considerable de gree that necessaryto maintain the armature in its picked-up position. In order for a trainshunt to be effective to release such a relay, the shunt must besufficiently low in resistance to shunt away from the relay winding theincrement of energy above the drop-away energy level of the relay. Suchshunt, however, provides a low resistance or short-circuit path acrossthe relay winding which maintains the flux in the relay for anappreciable interval of time, so that a correspondingly long timeinterval is required for a low resistance train shunt to lower theenergy level of the relay below its drop-away value. Various means havebeen proposed heretofore to accelerate the release of tractive armaturetype relays when shunted, and to provide relays having quick release,slow pick-up characteristics. My invention is directed to the provisionof novel and improved means for obtaining quick release characteristicsin relays having a pivoted tractive armature.

Another object is to provide novel and improved forms of electricalrelays particularly suitable for use as track relays in railway trackcircuits.

A further object is the provision of novel and improved means forobtaining quick release, slow pick-up characteristics in a relay havinga pivoted tractive armature.

An additional object is the provision of a relay of the pivoted tractivearmature type, having a drop-away level only slightly less than itspick-up energy level.

The above-mentioned and other important objects and characteristicfeatures of my invention which will become readily apparent from thefollowing description, are attained in accordance with my invention byproviding means for at times shifting the center of mass of the armaturemeans of the relay about the pivot of the armature. The arrangement issuch as to vary the moment arm of the center of mass of the arma turemeans, by shifting its mass center further away from the axis or pivotof the armature when it is picked up than when the armature is released,thereby to vary the torque required for operation of the armature means.

I shall describe one form of an electrical relay embodying my invention,and shall then point out the novel features thereof in claims.

In the accompanying drawing, Fig. 1 is a diagrammatic view of anelectrical relay embodying my invention. Fig. 2 is a top plan viewshowing a portion of the apparatus represented in Fig. 1. Figs. 3 and 4are sectional views, each taken on the line IIIIII of Fig. 2, showing inmore detail certain portions of the apparatus represented in Figs. 1 and2. In each of the several views, similar reference characters have beenemployed to designate corresponding parts.

Referring to the drawing, the reference characters l and la designatethe track rails of a stretch of railway track divided by insulatedjoints 2 into a track section DE. Section D-E is provided with a trackcircuit comprising a suitable source of current, such as a battery 3,connected in series with a resistor 4 across the track rails at one endD of the section, and the operating winding 6 of a track relay TRconnected across the track rails at the opposite end of the section.Relay TR comprises a magnetizable core 5 on which is mounted operatingwinding 5, and a tractive type armature l pivoted at 8. The relay, asshown, preferably includes also an auxiliary core 9 provided with anauxiliary winding [0 connected to a secondary winding H disposed on core5, and an auxiliary armature 52 connected to armature l by a rigidmember i3 preferably of non-magnetic material.

The relay further includes means operated by the armature for at timesshifting the center of mass of the armature means to alter its momentarm and thus vary the torque required to cause operation of the armaturemeans. These means comprise a movable weight which, as shown, preferablyconsists of an envelope or container I4 in which is disposed arelatively heavy movable mass which may, for example, comprise arelaatively dense liquid, such as mercury, partially filling thecontainer. The container is carried by armature i and is arranged tocause the heavy mass or liquid to move toward or away from pivot 8according as armature l is in its released or its picked-up position,respectively. As shown in Fig. 2, container is is supported by pivots ljournaled in the legs of a bifurcated portion of member 53. A bifurcatedor forked operating member it (see Figs. 3 and 4) secured to armature l,and fixed stops ill and it, are provided for causing container i l totilt, in a manner to be made clear presently.

When winding t is energized, as when section DE is unoccupied, armature'l is attracted to its upper position as shown in Fig. l, and containerid is caused to engage both front stop I? and leg 59 of operating memberiii, as can be seen in Fig. 3. In this position of the container, theliquid therein is at the left-hand end of the container (as viewed inFig. 3), or the end remote from pivot 8.

If, now, the relay is deenergized, as by a low resistance shunt placedacross winding 6 due to a train entering the section, armature l isreleased and drops to its back position. During the travel of thearmatur, container id remains in engagement with leg id of member ituntil the container engages back stop it. Further movement oi thearmature causes the container to rotate about its pivots it until thecontainer rests on the lower leg 26 of operating member it. his tiltingof the container of course causes the mercury therein to flow toward theright-hand end (as viewed in Fig. l), or to the end of the containernearest pivot 8 of armature i. Means, such as a baffle 25, may beprovided in the container to restrict the flow of the mercury to arelatively low rate.

In the released position of armature l, auxiliary armature i2 isdisposed adjacent auxiliary core 8, and when winding t again becomesenthe voltage induced in secondary winding H due to the growth of fluxin core 5, causes a current to how in winding 3. The flux due to thiscurrent in winding t threads armature i2 and opposes the tractive effecton armature l of flux due to current in winding 6. Armature accordinglyis retained in its released position til winding it becomes deenergizedwhen the nun in core assumes substantially a constant state condition,which condition substantially corresponds to the pick-up energy level ofthe relay. When this happens, armature l is caused to operate to itsupper position, as represented in Fig. l. Durin the upward movement ofthe armature, container it remains tilted against lower leg 23 of memberit until the container upper stop l'i and is rotated about its pivotsinto engagement with upper leg l9. rotation or tilting causes themercury to how back toward the left-hand or remote end or the container.

From the foregoing, it is readily apparent that have provided a movableweight on the armature of a relay and have provided means for shiftingthe resultant center of mass of the armature and weight, thereby varyingthe moment arm of such mass center to vary the torque to operate thearmature. When the sure is released and container M is tilted to d inthe drawing), the merthe ri cury therein is at the end or" the containernearest pivot 3, The resultant center or" mass of the armature andweight in this position of the armature; is, therefore, different fromthe resultant center of .mass of the armature and weight when thearmature is picked up and container id is tilted to the left so that themercury therein is at the end of the container remote from pivot 8. Thisshifting of the center of mass of the armature and weight of coursevaries the moment arm of the mass center about pivot t. The arrangementis such that the moment arm is greatest when the armature is picked up,hence, by shifting the mass center and varying its moment arm, thetorque required to hold up the armature may be adjusted to reach a valueonly slightly less than the torque required to pick up the armature whenits mass center is shifted in toward the armature pivot. Under suchconditions, it is apparent that even a low resistance shunt will causethe relay to release quickly, due to the fact that only a very smallincrement of energy above the hold-up level is available in the relay,and the flux accordingly will decay quickly to reach a value below thehold-up level, whereupon the armature drops away.

The use of retaining winding it makes the armature slow to pick up,hence the combination of the retaining winding and movable weightprovides a relay having the slow pick-up, quick release characteristicssought in a track relay. It is, of course, obvious that if slow pick-upcharacteristics are not desired, the etaining winding E9, secondarywinding ii and auxiliary armature it; may be dispensed with, in whichevent there will be provided a relay having ordinary pick-up andrelatively quick release characteristics when shunted.

In addition, it is readily apparent that if desired, the tiltablecontainer partially filled with mercury may be utilized also as acontacting device to close and open circuit connections in accordancewith the position of the mercury column. For example, the container maybe provided at either or both ends with contact ele ments (not shown)disposed to be immersed in and bridged by the mercury when the containeris tilted to cause the mercury to flow toward the elements. By properlypro-portioning the contact elements in such manner that they areimmersed only when the container assumes its position corresponding tothe picked-up or the released position of the armature, as the case maybe, slow acting contact arrangements may be provided in that thebridging (or closing) of the contact elements is delayed for theinterval required to operate the armature from one position to theother.

Although I have herein shown and described only one form of anelectrical relay embodying my invention, it is understood that variouschanges and modifications may be made therein within the scope of theappended claims without departing from the spirit and scope of myinvention.

Having thus described my invention, what I claim is:

1. In a tractive armature type relay, an electromagnet, a pivotedarmature biased by gravity away from said electromagnet, a movableweight carried by said armature, and means operable upon movement ofsaid armature for controlling said weight to shift the resultant masscenter of said armature and weight toward or away from said pivotaccording as said armature is released or picked up, respectively.

2. In a tractive armature type relay, an electromagnet, a pivotedarmature biased by gravity away from said electromagnet, a containercarried by said armature and partially filled with a relatively dense lquid, and means operable upon movement of said armature for causing saidliquid to flow toward or away from said pivot according as said armatureis released or picked up, respectively, whereby to increase the torquerequired to be exerted on the armature to maintain it picked up.

3. In a tractive armature type relay, an electromagnet, a pivotedarmature biased by gravity away from said electromagnet, a containerpivoted on said armature and partially filled with a relatively heavyliquid such as mercury, and means operable upon movement of saidarmature for tilting said container to cause said mercury to flow towardor away from said pivot according as said armature is released or pickedup, respectively, whereby to cause the pick-up and dropaway energylevels of the relay to be substantially equal in value.

4. A track relay having an electromagnet and an armature biased bygravity away from said electromagnet and pivoted for movement toward andaway from said electromagnet, an envelope pivoted intermediate its endson said armature for rotation in a plane perpendicular to the axis ofthe armature pivot and containing a relatively heavy mass movable towardone end or the other of said envelope, and means engaged during movementof said armature for rotating said envelope to shift said movable masstoward or away from said armature pivot according as said armature isswung away from or toward said electromagnet.

5. In a relay, an electromagnet, a pivoted armature biased by gravityaway from said elec= tromagnet, a container pivotally securedintermediate its ends to said armature and partially filled with arelatively heavy movable mass, two stops provided on said armature onefor engaging one end of said container when said container is tilted inone direction about said container pivot and the other stop disposed forengaging said one container end when said container is tilted in theopposite direction about said container pivot, and two fixed stops onedisposed for engaging the other end of said container during upwardtravel of said armature and the other of said fixed stops disposed forengaging said other container end during downward travel of saidarmature, said fixed stops being efiective to cause said container totilt toward or away from said armature pivot to cause said mass to movetoward or away from said armature pivot according as said armature isreleased or picked up, respectively.

6. A relay of the class controlled by the application of a lowresistance shunt placed across a pair of shuntable conductors whichconnect a source to the winding of the relay, comprising the combinationof, a relay winding, an armature means biased by gravity away from saidwinding and pivoted for swinging movement to- Ward and away from saidWinding, means carried by said armature means for shifting its center ofmass toward or away from the armature pivot according as said armatureis swung away from or toward said winding, respectively.

HAROLD G. WITIER.

